It is well known that in processes involving the combustion of liquid and gaseous hydrocarbons (such as methane) for the large-scale production of thermal and electrical energy, such as in thermoelectric power stations, one of the currently most serious problems is the release to atmosphere of the correspondingly large quantities of carbon dioxide produced by the combustion. Much comment has recently been made on the serious environmental problem of imbalance between the emission of CO.sub.2 into the atmosphere and the reuse of the same CO.sub.2 in the biosphere. In other words, the rate of combustion of carbon-based fossil fuels exceeds the rate of carbon fixation by photosynthesis in plants.
While fossil fuels (coal, natural gas and petroleum) constitute the main source of energy, it will not be possible to stop their production, although their consumption may have to be rationalized, even though it is probable that other forms of energy will be available in the future. Faced with the ecological risk associated with excess CO.sub.2 in the atmosphere, it has, for example, been proposed to increase the efficiency of direct utilization of solar energy or photosynthesis by selected micro-organisms which fix the CO.sub.2 and produce fuels (solar bioreactor).
However such a project has still to be developed and tried, and at the moment it is only a hypothetical solution.